1. Field of the Invention
The present invention is related to space station exit vehicles, and more particularly, to maneuvering an exit vehicle that is departing from a rotating space vehicle so that the exit vehicle is prevented from contacting the rotating space vehicle.
2. Description of Related Art
Dimensionally extended space vehicles, such as space stations, occupied by humans are becoming increasingly common during the present age of space exploration. Space stations, such as the International Space Station (ISS), provide living areas and work areas, such as laboratories, for use by the people temporarily residing in the space station. Such crews of individuals often stay on the space station for months at a time as they perform experimental tests, collect astronomical data, and coordinate other activities. These space stations often include exit vehicles, or crew return vehicles, that may be used by the crew during emergencies to depart the space station to rendezvous with another space craft or to return safely to earth.
Space stations such as the ISS typically have a stationary, or static, orientation during normal operation of the space station. Under such conditions, an exit vehicle may safely depart from the space station without being contacted by the space station. However, an emergency situation may arise wherein the space station is rotating about one or more axes. Emergencies that may cause the space station to spin may include an impact by one or more foreign objects, venting of pressurized gases due to pressure vessel rupture or puncture, or failure of control mechanisms of the space station. This rotating of the space station complicates the departure of the exit vehicle because the rotating space station could possibly contact the exit vehicle during departure. Such contact could damage the exit vehicle and/or the space station and threaten the lives of the crew in the exit vehicle. Therefore, a need exists for a safe and reliable method of maneuvering the exit vehicle from a rotating space station so that the exit vehicle does not contact the space station.
In addition, exit vehicles contain only a limited amount of propellant such as rocket fuel, which is primarily reserved for movement of the exit vehicle subsequent to departure from the space station. Such movement of the space station may include a rendezvous with another spacecraft or reentry of the exit vehicle into the earth's atmosphere. Devices such as the orbital maneuvering system (OMS) thrusters or the reaction control system (RCS) thrusters require propellant to move and orient the exit vehicle. The OMS thrusters provide relatively large amounts of thrust for large movements of the exit vehicle, while the RCS thrusters provide smaller thrust for finer movement of the exit vehicle. Both sets of thrusters enable precise maneuvering of the exit vehicle and are supplied by the limited amount of propellant. Therefore, the method of maneuvering the exit vehicle safely away from the rotating space station would preferably use a small amount of propellant during departure so that propellant is preserved for reentry or other maneuvering of the exit vehicle subsequent to departure from the space station. Similar needs exist for alternative space vehicles that comprise exit vehicles for the crew.
Therefore, a need exists for a method of maneuvering an exit vehicle from a rotating space vehicle so that the exit vehicle does not contact the space vehicle. Such a maneuver would advantageously preserve propellant for subsequent maneuvering of the exit vehicle.